Power amplifying apparatus for wireless transmitter

Abstract

A power amplifying apparatus according to the present invention can provide a stable electric power output with wide range by controlling both of the output amplifier for amplifying the electric power and the pre-amplifier disposed at the front of the output amplifier. Furthermore, in order to avoid the disadvantage that a transmission spectrum is expanded because of no supply of a stable voltage to be supplied to the electric power amplifier, thereby producing a cross-talk, a stabilizing power source circuit is provided to stabilize the voltage between the power amplifier and the power source for supplying the voltage.

We claim: 
     
       1. A power amplifying apparatus, comprising: power amplifying means having an input for receiving an input signal and a power source terminal for receiving a D. C. voltage, said power amplifying means for amplifying an amplitude component of the input signal on the basis of the D. C. voltage at said power source terminal; and   voltage stabilizing means having a battery source terminal for connection to a battery for receiving a battery voltage and an output connected to said power source terminal, said voltage stabilizing means for deriving and stabilizing a D. C. voltage from the battery voltage and supplying the stabilized D. C. voltage to said power source terminal in a feedback operation which feeds back and compares the D. C. voltage at said power source terminal with a D. C. reference voltage, wherein said voltage stabilizing means includes:   error detecting means having a first input for receiving the D. C. reference voltage, a second input for receiving the D. C. voltage present at said power source terminal and an output for producing an error difference voltage in dependence of a comparison between the D. C. reference voltage and the D. C. voltage at said power source terminal;   voltage supplying means having an input connected to said battery source terminal for receiving the battery voltage, a further input connected to the output of said error detecting means, and an output constituting the output of said voltage stabilizing means, said voltage supplying means for controlling the battery voltage to produce the stabilized D. C. voltage in dependence of the error difference voltage in a manner that drives the error difference voltage to substantially zero; and   voltage varying means connected to the second input of said error detecting means for adding a selectable D. C. voltage to the stabilized D. C. voltage at said power source terminal for selectively changing the error difference voltage which controls said voltage supplying means and thereby selectively changing the stabilized D. C. voltage.   
     
     
       2. The apparatus of claim 1, wherein said voltage supplying means comprises: a pulse width modulator having an input constituting the further input connected to the output of said error detecting means and an output for producing a pulse signal having a pulse width which is a function of the error difference voltage;   switching means having a first input constituting the input of said voltage supplying means for receiving the battery voltage, a second input connected to the output of said pulse width modulator for receiving the pulse signal and an output for producing the battery voltage switched on and off in accordance with the pulse signal; and   voltage converting means having an input connected to the output of said switching means and an output constituting the output of voltage supplying means, said voltage converting means converting the switched battery voltage into a D. C. voltage which constitutes the stabilized D. C. voltage supplied to said power source terminal.